Graph API

[thedodd]

First, thanks for all of the excellent work on this! I have a workload which could benefit from the Graph API (as opposed to just using individual stream submissions and such).

Any ideas on LOE to implement, what current blockers are, and so on?

Perhaps we can discuss what getting started on implementing this should look like, desired API style, and all that.

[RDambrosio016]

I started some WIP graph stuff a while ago to see what the API was like, and from what i can tell there is basically no way to make it safe because of the sheer amount of things that could go wrong. The graph API is also large, really large. I will probably not focus on graphs for a while since there are much more pressing features that need attention, but if anyone would like to work on it i would be happy to review any PRs or talk about it.

[thedodd]

By your analysis, is stream capture (for graph building) the main source of unsafety? Or is it more broad than that (such as standard graph building and execution)?

[RDambrosio016]

graphs combine the most unsafe parts of CUDA in one very dangerous package:

• Stream ordering semantics that can't be checked by a library (easily and without overhead)
• Kernel launches
• Asynchronous stuff
• Unsafe details, such as "this works with stream capturing", "this does not work with stream capturing", "this is ub when using stream capturing". For example IIRC using texture or surface refs in a kernel in a capture is UB.